Lecture: The Avian Respiratory System
Anatomy
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nostrils
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trachea
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bronchi
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lungs: bronchi that bring air to lungs divided into many smaller tubes;
lung made up of many tiny tubes (unlike mammals, whose lungs are made of
tiny, dead-end sacs) that run through the lung, and through which air passes.
Tubes contact capillaries for gas exchange.
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air sacs: sacs attached to lungs, bronchi, into which air passes during
parts of breathing. In neck, front of body, upper chest, abdomen;
some extend into bones, syrinx. Function in allowing efficient air-flow
through lungs, help remove heat produced by high metabolism during flight,
cushion internal organs during flight, sound production.
Function: Air Flow Through Lungs
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inspiration (breathing in): air passes into air sacs
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expiration (breathing out): air passes through lungs, and out
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the breathing cycle: movement of air through lungs (see Figure 1)
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result: efficient, one-way air flow through lungs; almost no dead air space
in lungs
Figure 1. Movement of a "slug" of air through the respiratory system
of a bird